Microstructure, phase evolution and corrosion behaviour of the Zn-Al-Mg-Sb alloy coating on steel

In the present work, the influence of antimony (Sb) addition in Zn-Al-Mg alloy on the microstructure, phase characteristic, solidification behaviour and corrosion resistance of hot dipped Zn-0.5Al-0.5Mg-xSb (x = 0, 0.1, 0.3 and 0.5 wt-%) coated steel wires were evaluated. Thermal analysis revealed that cooling rate of the liquid metal using the steel mould (5.3 degrees C s(-1)) was higher than using ceramic mould (0.3 degrees C s(-1)). Based on the phase analysis and verified by thermodynamic calculations, it was revealed that Zn11Mg2 and Zn2Mg phases appeared for Zn-Al-Mg alloy at slow and fast cooling rates while, the Mg3Sb2 phase was observed after addition of Sb at both cooling rates. Corrosion behaviour of the alloys determined through electrochemical measurements shows that Zn-Al-Mg alloy with 0.3 wt-%Sb has the lowest corrosion rate indicating an excellent corrosion resistance.